Physics Paper 2

Cards (32)

  • Sound waves are an example of longitudinal waves.
  • CONTACT FORCE: when objects are physically touching eg. reaction force, friction, tension.
    NON-CONTACT FORCE: without objects physically touching eg magnetism, electrostatic force and gravity a VECTOR is a quantity with MAGNITUDE & DIRECTION. a SCALAR is a quantity with MAGNITUDE only.
  • here, gravitational field strength is 9.8N/g. that means every 1kg has a weight of 100.
    WORK DONE just means energy transferred by a force. this means that if you hold an object or lift at A CONSTANT
    speed, you must be pushing upwards with a force that's the same size as its weight!
  • any object that deforms ELASTICALLY (returns to its original shape) obeys HOOKE'S LAW
    force is directly proportional to extension.
    gradient = spring
    constant.
    PRACTICAL:
    add masses onto spring to change force.
    • measure extension with ruler at each weight, plot f against e.
    • gradient of graph = spring constant.
    • avoid systematic error by lining up 0cm with bottom of spring.
    • avoid parallax error by getting on eye level when measuring
  • the GRADIENT of a DISTANCE/DISPLACEMENT-
    TIME graph gives you
    the SPEED/VELOCITY.
  • the gradient of a SPEED/VELOCITY - TIME graph is ACCELERATION
    while the area under the graph gives you DISPLACEMENT.
  • NEWTON'S 1st LAW: if no resultant force acts on an object, its motion will be constant (velocity will not change).
    NEWTON'S 2nd LAW: F= ma
    NEWTON'S 3rd LAW: for every action (force), there is an equal and apposite reaction (force).
  • F= ma PRACTICAL:
    • accelerate the trolley on track with slotted mass on string over pulley.
    • use lightgate to measure acceleration.
    • change force by removing masses and placing on trolley to keep total mass the same.
    • use f= ma.
  • STOPPING DISTANCE = THINKING + BRAKING.
    THINKING DISTANCE is affected by;
    • speed (proportional)
    • distractions
    • alcohol
    • alcohol
    • tiredness
    STOPPING DISTANCE
    is affected by:
    • speed
    • condition of brakes, tires and road
    • weather conditions
  • momentum= mass x velocity
    in any collision, TOTAL MOMENTUM iS ALWAYS CONSERVED.
    TYPES:
    rebound
    coupling
    recoil
  • WAVES
    transfer ENERGY without transferring MATTER
    LONGITUDINAL WAVES: direction of oscillation is PARALLEL with the direction of energy transfer (eg sound, seismic). consists of COMPRESSIONS AND REFRACTIONS
    TRANSVERSE WAVES: the direction of oscillation is PERPENDICULAR with the direction of energy transfer (eg water, light, EM).
  • WAVES PRACTICALS
    SOUND
    • someone makes a noise whilst standing within proximity of a wall. another person starts a stopwatch when they hear it, stopping it when the sound echoes and they hear it again.
    • LIQUID
    • ripple tank, light above, paper below. motor-powered dipper on the surface.
    • take photos/videos to measure frequency and wavelength.
    • change motor speed and repeat.
  • SOLID
    • attatch string to a vibrator /energy generator, pulling it tout with a ramp and adding masses to the end.
    • measure wavelength with a metre ruler.
    • frequency changed by adjusting generator, adjust tension by changing masses (depends what you’re investigating)
    • put into equation.
  • all EM waves are EMITTED and ABSORBED by ELECTRONS
    except for gamma. they’re emitted by nuclei
  • if the ENERGY of the wave is high enough it can cause an electron to leave its atom leaving an ion. UV and GAMMA are worst
  • RADIO WAVES
    phone, wifi
    MICRO WAVES
    cooking, absorbed by H2O
    INFARED
    cooking, absorbed by surface
    VISIBLE LIGHT
    vision
    ULTRAVIOLET
    tanning, can cause cancer
    X RAYS
    medical scans, dangerous
    GAMMA RAYS
    sterilisation, medicine, dangerous
  • PRACTICAL:
    show that MATTE BLACK is the best emitter and absorber of IR: use LESLIE CUBE with THERMOMETER or tubes wrapped in different materials under the source .eg. IR lamp. SHINY materials are the WORST emitters and absorbers
  • When waves enter a new MEDIUM (material) their SPEED changes, as does their ANGLE.
  • if SPEED decreases, WAVELENGTH does, whilst FREQUENCY remains constant. we only need to draw the RAYS, not the WAVEFRONTS
  • if the wave slows down, it bends towards the NORMAL (eg going from air into another material)
  • the angle of REFRACTION is SMALLER than the angle of INCEDENCE
  • when the light exits, it speeds up again and bends AWAY from the NORMAL
  • PERMANENT magnets always produce a magnetic field whereas INDUCED magnets become magnetised when in another magnetic field.
  • mini compasses or iron filings can be put in a magnetic field to visualise it. we always draw the field lines going from North to South pole.
  • IRON, COBALT and NICKEL are magnetic (can become induced magnets) and so are attracted
    to permanent magnets. Other metals aren't.
  • a CURRENT CARRYING wire in a MAGNETIC FIELD will experience a force (as it produces its own magnetic field that will interact with the other).
  • PRACTICAL
    FINDING MAGNETIC FLUX DENSITY
    • place magnet on balance.
    • tare balance, measure mass when known current flowing.
    • convert to newtons.
    • measure lenath of wire in field.
    • rearrange f=BIL to calculate B.
    right hand rule= current in wire.
    left hand rule = direction of force.
  • motors use the motor effect, both sides of a coil experience a force in opposite directions, and it turns.
  • TO INCREASE SPEED (motor effect):
    •add more turns to the coil
    increase voltage/current
    • use a stronger magnet
  • a SPLIT RING COMMUNICATOR is used to ensure that the current is reversed every half turn to keep the coil spinning
  • LOUDSPEAKERS use the motor effect:
    a current is sent from the source, causing the COIL and SPEAKER CONE to vibrate, sending sound waves